1. Field of the Invention
The present invention relates to an ink container and an ink container-sealing wrapper assembly.
2. Discussion of Related Art
In general, in, an ink-jet recording method, droplets of ink are formed by various ink ejecting methods and a portion or all of the ink droplets are fixed or sprayed on a recording medium such as a sheet of paper to perform printing. There are known various ink ejecting methods such as a method of electrostatically sucking ink, a method of mechanically oscillating or displacing ink by using piezoelectric elements, a method of heating ink to generate air bubbles and ejecting the ink by a pressure produced when the ink is bubbled. In a printing head of an ink-jet recording apparatus which utilizes the piezoelectric elements as described above, the amount of electric power consumption is smaller than in the method that utilizes the pressure produced upon generation of the air bubbles by application of heat to the ink. In addition, the printing head which utilizes the piezoelectric elements is advantageous in that the stability of the ink with respect to heat can be ignored since the ink is not exposed to heat.
A water-based ink for such, an ink-jet recording apparatus is known and practically used. The known water-based ink is prepared by dissolving or dispersing various water-soluble dyes or pigments in water or an aqueous medium including water and a water-soluble organic solvent. Such water-based ink for ink-jet recording is needed to exhibit optimum properties and characteristics as follows: The ink has a good introduction property that permits the ink to be easily introduced into nozzles of a printing head of the ink-jet recording apparatus. The ink does not cause any clogging at the nozzles and in ink channels which arises from agglomeration or precipitation of the components in the ink, and has good ejection performance. The ink assures a high degree of print quality. The ink does not cause corrosion of components or materials of the ink-jet recording apparatus which are formed of metal, resin, adhesive agent, etc.
The water-based ink for ink-jet recording is manufactured by a process including a step of dissolving or dispersing an ink material including a dye or a pigment in a solvent and a step of filtering a solution of the ink material. Where the ink as manufactured by the process is contained in a package for use on the ink-jet recording apparatus, oxygen dissolved in the ink deteriorates a part of the ink material, so that the ink cannot maintain its optimum properties and characteristics for a long period of time. Especially where the ink material includes glycol ethers or surfactants having polyoxyethylene chains, the ether link portions of those materials and the oxygen dissolved in the ink are subjected to autoxidation, thereby undesirably causing changes in the properties of the ink, or producing agglomerates or deposits. In this case, the ink suffers from deterioration in its introduction property and ejection property. Further, the printing quality is undesirably lowered. In addition, aldehydes, carboxylic acids, etc., generated by autoxidation deteriorate the coloring material of the ink, and cause corrosion of metallic materials of the components of the ink-jet recording apparatus. Thus, the oxygen dissolved in the ink causes a risk of considerably deteriorating reliability of the ink-jet recording apparatus.
To avoid the drawback described above, it has been practiced to carry out a deaerating or degassing treatment of the ink, so as to remove the oxygen dissolved in the ink before the ink is accommodated in a package. This deaerating treatment involves, for instance, an operation to stir the ink within a pressure vessel at a reduced pressure and an operation using a deaerating device equipped with a gas permeation membrane.
In general, since the package for accommodating the deaerated ink is a box-like container obtained by injection molding of resin such as polypropylene or polyethylene, or a bag obtained by welding laminated films of resin such as polyester or polyamide, such a container or a bag used as the package for accommodating the deaerated ink has a slight degree of gas permeation. Accordingly, it is impossible, from the standpoint of cost, to store the ink in a fluid-tightly accommodated state for a long time period while being isolated from the outside air. Even where the deaerated ink is accommodated in the package described above, the air inevitably enters the package with a lapse of time, so that the air including the oxygen is again dissolved in the ink, whereby the properties and the characteristics of the ink are gradually deteriorated.
JP-B2-3-61592 discloses a technique to prevent the oxygen from being dissolved again in the deaerated ink. According to this technique, an ink container filled with the deaerated ink is accommodated in a sealing container, and the sealing container is kept under a reduced pressure during transportation or storage. In installing the ink container on the ink-jet recording apparatus, however, the ink container needs to be taken out of the sealing container. After the ink container has been installed on the ink-jet recording apparatus, it is impossible to prevent the air from being dissolved in the ink, so that the properties and characteristics of the ink are inevitably deteriorated.